Technical Field
The present invention relates to a thermoplastic polyurethane composition for injection molding and a method of manufacturing the same. More particularly, the present invention relates to a thermoplastic polyurethane composition for injection molding, which is capable of being easily injection-molded since a slip property is imparted to a soft segment, and possessing excellent durability properties such as heat-aging resistance, photoaging resistance, and wear resistance, and stability properties such as airbag deployment performance and anti-fogging property, as well as excellent tactile sensation and embossing quality, when a chain extender and a multifunctional polydimethylsiloxane-based compound are mixed with an isocyanate- and ether-containing polyester polyol, and can be useful in simplifying processes, reducing manufacturing costs, and simplifying facilities due to a decrease in the number of parts when molded articles are manufactured using the composition, and a method of manufacturing the same.
Background Art
A method of processing a soft type of a skin material for crash pad panels of interior parts of a vehicle includes techniques such as vacuum molding, powder slush molding (PSM), reaction injection molding (RIM), laminate insert molding (LIM), leather wrapping, etc. Here, the skin material for panels refers to a soft pad type of a skin material, and is located on a core material and a pad material.
However, the above-described processing methods use a very restricted material to be applied, and have the following problems in terms of techniques. Specifically, the vacuum molding technique has a problem in that it has limited design flexibility, and it is difficult to realize fancy embossed features.
The PSM technique has problems in that manufacturing costs are high due to a complicated process of preparing a material, and the initial investment costs required to construct facilities are high. Products produced by the PSM technique advantageously have high design flexibility, but have problems in that it is impossible to completely remove tiny pinholes formed on a surface thereof due to their molding properties due to the presence of slush, and there are a relatively large number of redundant skirts. In addition, it has a drawback in that the energy cost is high due to a relatively long cycle time and high process temperature. In addition, thermoplastic polyurethanes (TPUs) prepared by typical polymerization methods other than water dispersion polymerization for application to PSM techniques have a drawback in that an increase in cost of raw materials may be caused since a process of freeze-pulverizing TPU to prepare a powder is further used.
The RIM technique has an advantage in that lightweight, thin and flexible products may be easily painted and molded, but has drawbacks in that a cycle time is long, and raw materials are expensive, compared to an injection technique.
As the first technique developed by Visteon Corporation (US), the LIM technique is an integrated molding technique which includes vacuum-molding a sheet on which a skin material/foam layer is laminated to prepare a skin material, inserting the skin material in a C/pad injection mold, and resin-injecting the skin material to prepare a crash pad. A PP foam layer has a drawback in that emotional qualities may be degraded due to compression by an injection pressure.
The leather wrapping advantageously imparts a refined appearance to interior parts, but has a drawback in that labor costs are high.
As such, a technique of processing a soft type of a skin material using the above-described processing methods has problems in that types of materials applicable thereto are highly restricted, and it is very difficult for materials of the same type to retain good aesthetics, have excellent durability under high-temperature and UV-radiation environments, satisfy deployment performance of airbags, and simultaneously meet both emotional qualities and comfort properties (low VOCs).
In addition, although there are materials which satisfy all physical properties, long-term durability, reliability performance, and emotional qualities, all of which are required for soft types of skin materials for crash pad instrument panels, a very limited number of the materials may be injected into skin materials for instrument panels (IPs) as thin films (1 mm), with no gas flow marks and weld lines formed on an appearance thereof, without performing a molding process. Here, since the IP skin materials themselves are thin, relatively large in size, and have regions which are difficult to design, such as curved regions, etc., typical thermoplastic resin materials may suffer from appearance-related problems in that short molding, gas flow marks, weld lines, and sink marks may be formed on surfaces of the IP skin materials when these resin materials are injection molded.
Korean Registered Patent No. 0351742 discloses a molded article including a thermoplastic polyurethane composed of ether-containing polyester polyols. However, a molded article formed of the skin material for instrument panels prepared by the PSM technique has drawbacks in that a process of preparing a skin material is complicated, manufacturing costs are high, and initial investment costs required to construct facilities are high.
In addition, Korean Registered Patent No. 0493231 discloses a composition for improving scratch resistance of TPU for instrument panels. However, external migration into foam inside or outside the skin material may occur since an additive is not bound to chains via chemical bonds present in a molecular structure of TPU. Therefore, the composition has a drawback in that anti-scratch properties and wear resistance may be degraded over time.
Therefore, there is a demand for development of novel materials which have excellent durability under high-temperature and UV-radiation environments, and are applicable to injection molding while satisfying both emotional qualities and comfort properties.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.